1. Field of the Invention
The disclosed technology relates to an enhancement mode III-nitride device and a method for manufacturing thereof.
2. Description of the Related Technology
AlGaN/GaN high electron mobility transistors (HEMTs) are now receiving great attention because of their potential applications to high-power and high-frequency devices.
Enhancement mode GaN HEMT devices can be realized by depletion of the two-dimensional electron gas (2DEG) using a p-type doped GaN or AlGaN layer above the channel.
Typically, this layer is grown during the metal-organic chemical vapor deposition (MOCVD) process of the complete GaN/AlGaN composite stack for buffer, channel and barrier layers, with the p-GaN blanket on top of the AlGaN. However, further device fabrication requires the p-GaN layer to be selectively etched from the AlGaN barrier in all regions except the channel region.
The etching of p-GaN selective to AlGaN is both difficult and leaves the surface between gate and drain exposed to the plasma etch. This region is no longer passivated after this etch step, which makes it difficult to use high temperature dielectric deposition to passivate the surface. As a result, this device architecture is subject to drain lag. The term “drain-lag” is used to describe the slow transient response of the drain current when the drain-source voltage is pulsed.